I've noticed while precipitant in 10X and 1X TBST buffers in my lab. I can't quite say for sure whether they're the same precipitant or different types. I would like to ask whether they might be signs of microbial contamination.
From what I've read so far it seems 10X TBST should have sufficiently high osmotic pressure to prevent microbial growth, is that correct?
As for 1X TBST, I was under the impression that Tween-20 being a detergent grants a certain degree of protection against contamination. Is the concentration (0.1%) simply too low for it to matter or is Tween-20 unable to provide contamination regardless of concentration 🤔?
I've attached images bellow, the plastic bottle holds 1X TBST and the cylinder 10X TBST.
1X TBST composition:
- Tris: 20 mM
- NaCl: 150 mM
- Tween 20 detergent: 0.1% (w/v)
The osmolarity of 1X TBST is definitely not high enough to prevent growth of microorganisms, nor is the pH likely high enough to discourage them. The 10X TBST might slow them down because of the high-ish salt concentration. Both the Tris and the Tween could be sources of carbon for growth of microorganisms.
The stuff in the top picture looks biological. The stuff in the bottom picture at the bottom of the cylinder looks like an undissolved compound.
If you plan to store buffers containing organic compounds for any length of time, you should filter-sterilize them, and preferably keep them refrigerated.
Based on the way the smears are present on the sides of container it does look rather like some kind of contaminant, or it could be precipitation. If you have access to a microscope you could take a quick look. When was the buffer made? I've seen fungus growing in "20% bleach" that someone made and forgot on a shelf for a year or so.
Adam B Shapiro Thank you very much for the answer Mr. Shapiro. I will be storing my 1X buffer in 4°C from now on.
@ Amy Klocko Wow, fungal growth in bleach sounds busted. I believe the 1X buffer in question is perhaps 2 weeks to 1 month old. In future I'll check with microscope, thanks for the heads up.
Amy Klocko Wow, fungal growth in bleach sounds busted. I believe the 1X buffer in question is perhaps 2 weeks to 1 month old. In future I'll check with microscope, thanks for the heads up.
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